Truck trailers are conventionally made to haul either exclusively dry freight or exclusively liquid or fluid freight. The dry freight trailer conventionally consists of an elongated generally rectangular trailer body having rear and sometimes side doors for loading and unloading. Liquid or fluid trailers conventionally consist of tanks or hoppers loaded from the top and unloaded from the bottom.
The liquid freight tankers often deliver their loads to destinations where dry freight could be picked up and returned to the point of origin. However, since dry freight cannot be handled, the tankers must either dead head back to the point of origin or must dead head to another source of fluid freight. Similar load and dead head factors exist in hauling dry freight in trailers. Dead heading is obviously inefficient from equipment, energy utilization and cost standpoints.
Previous attempts have been made to provide a trailer capable of universally handling either dry or liquid freight. In one such attempt, a collapsible rubber reservoir was used which occupied little space when dry freight was carried and could be filled for liquid freight. This rubber reservoir attempt was generally unsuccessful for several reasons. For example, the rubber reservoir was hard to load and unload, was hard to clean and was difficult to handle because of its bulk, weight and flexability. Moreover, the rubber reservoir, when filled, was not particularly stable and the liquid load had a tendency to shift affecting the load balance and force distribution on the trailer.
In a second attempt, a central fluid hopper was employed with fore and aft dry freight storage compartments positioned generally beneath the converging hopper walls. This attempt was also generally unsuccessful for several reasons. For example, the limited volumes of liquid or dry freight that could be handled were not cost effective and the dry freight was difficult to load and unload because of the position and limited volume of the two compartments and limited access to the two compartments for loading and unloading.
Recently, the rules and laws governing trailer size and weight have been modified to allow increased trailer width, length and height and increased unloaded and loaded trailer weight. Federally, a trailer may now be 48 feet long, 13 feet-6 inches high and 102 inches wide, and the entire loaded weight of the tractor and trailer may be 80,000 pounds. Applicant has considered these new volume and weight regulations in developing the trailer of the present invention.